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From:   Anup Patel <anup@brainfault.org>
Date:   Tue, 13 Jun 2023 10:12:40 +0530
Message-ID: <CAAhSdy2p6K70fc2yZLPdVGqEq61Y8F7WVT2J8st5mQrzBi4WHg@mail.gmail.com>
Subject: Re: [PATCH v3 02/11] of/irq: Set FWNODE_FLAG_BEST_EFFORT for the
 interrupt controller DT nodes
To:     Saravana Kannan <saravanak@google.com>
Cc:     Anup Patel <apatel@ventanamicro.com>,
        Rob Herring <robh@kernel.org>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Marc Zyngier <maz@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Atish Patra <atishp@atishpatra.org>,
        Andrew Jones <ajones@ventanamicro.com>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org, iommu@lists.linux.dev
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On Sat, Jun 10, 2023 at 2:47=E2=80=AFAM Saravana Kannan <saravanak@google.c=
om> wrote:
>
> On Fri, Jun 9, 2023 at 4:40=E2=80=AFAM Anup Patel <apatel@ventanamicro.co=
m> wrote:
> >
> > On Fri, Jun 9, 2023 at 1:35=E2=80=AFAM Saravana Kannan <saravanak@googl=
e.com> wrote:
> > >
> > > On Thu, Jun 8, 2023 at 11:28=E2=80=AFAM Rob Herring <robh@kernel.org>=
 wrote:
> > > >
> > > > +Saravana
> > > >
> > > > On Mon, May 08, 2023 at 07:58:33PM +0530, Anup Patel wrote:
> > > > > The RISC-V APLIC interrupt controller driver is a regular platfor=
m
> > > > > driver so we need to ensure that it is probed as soon as possible=
.
> > > > > To achieve this, we mark the interrupt controller device nodes wi=
th
> > > > > FWNODE_FLAG_BEST_EFFORT (just like console DT node).
> > > > >
> > > > > Fixes: 8f486cab263c ("driver core: fw_devlink: Allow firmware to =
mark devices as best effort")
> > > >
> > > > It is good practice to Cc the commit author of what you are fixing.
> > > >
> > > > > Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> > > > > ---
> > > > >  drivers/of/irq.c | 10 ++++++++++
> > > > >  1 file changed, 10 insertions(+)
> > > > >
> > > > > diff --git a/drivers/of/irq.c b/drivers/of/irq.c
> > > > > index 174900072c18..94e1d9245cff 100644
> > > > > --- a/drivers/of/irq.c
> > > > > +++ b/drivers/of/irq.c
> > > > > @@ -535,6 +535,16 @@ void __init of_irq_init(const struct of_devi=
ce_id *matches)
> > > > >       INIT_LIST_HEAD(&intc_desc_list);
> > > > >       INIT_LIST_HEAD(&intc_parent_list);
> > > > >
> > > > > +     /*
> > > > > +      * We need interrupt controller platform drivers to work as=
 soon
> > > >
> > > > If it's platform drivers/devices you care about, then perhaps this
> > > > should be done when platform devices are created.
> > > >
> > > > > +      * as possible so mark the interrupt controller device node=
s with
> > > > > +      * FWNODE_FLAG_BEST_EFFORT so that fw_delink knows not to d=
elay
> > > > > +      * the probe of the interrupt controller device for supplie=
rs
> > > > > +      * without drivers.
> > > > > +      */
> > > > > +     for_each_node_with_property(np, "interrupt-controller")
> > > >
> > > > This function only operates on nodes matching 'matches', but this
> > > > operates on everything.
> > > >
> > > > It does make sense that if we init an interrupt controller here, th=
en we
> > > > will surely want to probe its driver later on. So maybe just move
> > > > setting FWNODE_FLAG_BEST_EFFORT within
> > > > for_each_matching_node_and_match() below.
> > > >
> > > > > +             np->fwnode.flags |=3D FWNODE_FLAG_BEST_EFFORT;
> > > > > +
> > >
> > > Definite Nack. You are pretty much disabling fw_devlink for all
> > > interrupt controllers. There are plenty of examples of the IRQ driver=
s
> > > being needed very early on and still probing properly without the nee=
d
> > > for this flag. Please fix your driver/DT.
> >
> > Okay, I will try to set FWNODE_FLAG_BEST_EFFORT only for
> > APLIC device_node via IRQCHIP_DECLARE().
>
> No, my point is that you very likely don't need to use that flag.
>
> What exactly is the problem you are facing? Point to an example RISC-V
> dts (not dtsi) in upstream and give specifics please.

The APLIC irqchip driver added by this series is a platform driver. It
used to work fine without setting FWNODE_FLAG_BEST_EFFORT
flag in fwnode but after commit 8f486cab263c the APLIC irqchip
driver did not probe hence this fix.

Regards,
Anup